1. Field of the Invention
The present invention relates to a question and answer system (hereinafter referred to as expert system) capable of processing a medical diagnosis, a failure diagnosis, an integrated circuit designing, scheduling and the like, and more particularly, to an improved display system of the inference process (trace) of a question and answer system having forward and backward inference control methods.
2. Description of Prior Art
An expert system easily capable of processing a medical diagnosis, a failure diagnosis, a scheduling and the like has been directed people's attentions in various fields. Therefore, expert systems of various types are proposed. It is now possible to construct an expert system using a small computer such as a personal computer owing to the improvement of an integrated circuit according to the development of a semiconductor technique. Under these circumstances, people buy expert shells from manufacturers and input the information of rules and facts into expert systems so as to construct expert systems of their own. It is indispensable that an expert system has a function of easily and correctly displaying an inference process (trace) as well as an inference execution.
The following three are displayed as the inference process in the expert system having a forward inference method:
(1) executed rules PA1 (2) change (addition or deletion) of a working memory PA1 (3) change (addition or deletion) of executable rules
There is a case in the above (3) in which a rule is unexecutable because the condition of a negation is not satisfied although all the conditions of an acknowledgement are satisfied.
A conventional expert system has a problem in that it has no function for indicating that a rule is unexecutable because of the condition of a negation not being satisfied, which causes a user to wonder why the rule is unexecutable.